Atomic-scale reconstruction of oxide driven by oxygen transfer at AlN-capped GaN interfaces revealed through molecular dynamics simulations

Abstract

This study reports the elucidation of atomic-scale reconstruction mechanisms at the AlN/GaN interface with native gallium oxide by means of molecular dynamics simulations based on a novel charge-transfer-type interatomic potential for the Ga–Al–O–N quaternary system. Optimized against over 21 000 configurations calculated via density functional theory, this potential accurately describes bond breaking and formation across crystalline and amorphous phases, enabling the analysis of transient interfacial processes that are difficult to resolve experimentally. The reliability of the potential was validated by simulating the initial oxidation of AlN surfaces; molecular dynamics simulations successfully reproduced the orientation-dependent kinetics, yielding ordered Al–O bilayers and O–Al–O trilayers on AlN(0001) that quantitatively match scanning transmission electron microscopy observations. Applying this framework to the AlN/GaOx/GaN interface, we investigated the structural evolution under thermal annealing. Oxygen atoms spontaneously migrate from the native gallium oxide layer to the AlN cap, driven by the thermodynamic stability of Al–O bonds rather than Ga–O bonds. This reaction effectively reduces the residual gallium oxide, transforming the interface into a chemically stable (Ga,Al)NxOy transition layer. These findings provide an atomic-scale depiction of interfacial reactions in AlN-capped GaN metal–oxide–semiconductor field effect transistors, offering mechanistic insights into processes that are not directly accessible by conventional experimental techniques. The insights may also provide guidance for understanding interfacial phenomena in other heterogeneous material systems.